This invention relates to power actuated fifth wheel hitches, and more particularly to series actuator controls in series inside and outside the tractor cab for power actuation of the hitch.
Highway type semi tractor and trailer combinations predominantly use fifth wheel hitches for coupling. Receipt and coupling by the fifth wheel hitch of the kingpin occurs automatically when the two are in proper alignment. Release of the hitch from the kingpin is achieved by manually pulling a release rod under the trailer, the rod compressing the actuator spring and allowing one or both hitch jaws to retract. This release rod projects from the centrally located hitch toward the side of the trailer, but normally terminates short of alignment with the wheels in order to prevent damage to the release rod from objects traveling around the tires or from a retread which may tear loose from the spinning tires. Although reaching under the trailer and applying a powerful pull on the release rod has not always been too much of a problem with typical large male drivers, recent legal changes in the trailer width allowed and in the type of drivers entering the field are causing the manual release to be a problem. More specifically, trailers in many areas can now be legally as wide as 102 inches rather than the 96 inch previous standard. Consequently, the manual release rod is a considerably larger distance beneath the wider trailers, i e , spaced from the side of the trailer body. Also, there are more women drivers and more drivers of smaller stature and shorter arms such as those of Asian extraction. Consequently, the driver has more difficulty reaching far enough under the trailer to grasp the handle of the release rod, and even greater difficulty pulling it hard enough to release the hitch. In some trailer arrangements, there is no room for reaching in to grasp the handle of the release rod.
Conceivably, the release could be power actuated. Power actuated fifth wheel hitch releases have been used heretofore on truck tractors limited to yard work, i.e., moving trailers in the storage yard. These typically employ a fluid cylinder to release the jaws. A control actuator in the cab, e.g., a push button or switch, is simply pressed or shifted to actuate the fluid cylinder and release the hitch. As far as is known, however, such power actuators for release have not been employed on highway tractors. Accidental actuation of the fluid cylinder as by bumping the switch, or absent-mindedly pushing the switch, or the like, causing hitch release while traveling high speed highways or busy streets, could be disastrous.